Cerebellar GABAergic processes: evidence for critical involvement in a form of simple associative learning in the rabbit.

Converging evidence from electrophysiological recording and lesion studies suggests an essential role for the cerebellum in classical conditioning of the nictitating membrane response in the rabbit. The present study begins to delineate within this structure neurotransmitter systems that appear critical for the expression of this form of simple associative learning. Experiments reported here demonstrate that microinfusion of gamma-aminobutyric acid (GABA) antagonists (either bicuculline methiodide or picrotoxin) into specific areas of the medial dentate/lateral interpositus nuclei or into the cerebellar cortex of lobule HVI can selectively and reversibly abolish conditioned responding, while leaving the unconditioned reflex response intact. The results are consistent with the suggestion that GABAergic synapses play an essential role in the circuitry that mediates the conditioned response.